The logarithmic-length conjecture for binary words with a prescribed number of subsequences
The logarithmic-length conjecture for binary words with a prescribed number of subsequences
A binary word is a finite word over the alphabet . For a binary word , let denote its number of nonempty subsequences.
Logarithmic-length conjecture. For every integer , there exists a binary word such that
and
The Fibonacci-type alternating words show that any binary word with exactly subsequences must have length , so the conjecture asks whether this lower bound is sharp up to a constant factor. The source does not provide a resolution.
Sources & referencesView supporting material
Primary source
Radosław Żak, “Finding binary words with a given number of subsequences”, arXiv:2210.00342 (2022).
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